Decoding ROM labels

Back in the earliest days of the RC2014, it came with a pre-programmed 27C512 64k ROM, with Microsoft BASIC on it in the first 8k, and it would work with 32k of RAM and a 68B50 ACIA. One set up, one ROM, life was simple!

As time has gone on, and more options have become available, other ROM images, such as Microsoft BASIC for 56k RAM, CP/M Monitor, RomWBW and Small Computer Monitor have been introduced. See this page for a brief overview of each option

Future possibilities, such as other UARTs, different CPUs or other variations will inevitably lead to more ROM images being needed. So, in order to keep track of what is programmed where, ROMs are now being shipped out with a label on them.

27C512 64k ROM

Every 64k ROM now has an 8 digit code on it. Each digit, from left to right, refers to an 8k bank from 0x0000 to 0xD000. This bank can be selected with the A13, A14, A15 jumpers;

Address

A15

A14

A13

ROM Label

0000

0

0

0

Xooooooo

2000

0

0

1

oXoooooo

4000

0

1

0

ooXooooo

6000

0

1

1

oooXoooo

8000

1

0

0

ooooXooo

A000

1

0

1

oooooXoo

C000

1

1

0

ooooooXo

E000

1

1

1

oooooooX

The value of the digit represents the ROM image that sits in that particular 8k bank. Currently, it will be one of the following;

With the advent of the 512k ROM 512k RAM Module, an ST39SF040 is now supplied. This will have the designation of x.512K, where x is the software designation. At time of writing, only 8 image options are available;

Note that despite having total control over which designation I want to use for whichever ROM image and where that is located on the ROM – I still managed to pick a combination that my label gun was unable to do! So some people will have a label that starts with an interlocking “n” and “u” character, which is the closest I could do to represent a “2”. If this is the case, your “¬4006000” is actually “24006000”. In order to get around this, I have now bought an extra 2 label guns, which have been dismantled to allow the belts to be swapped around, and reassembled. Normally reassembly of label guns is only possible by a highly skilled and qualified octupus, so I don’t recommend anybody tries doing this themselves!